Method for producing hydrocracked lube oil products

ABSTRACT

The production of lube oil product by hydrocracking is made more selective and commercially attractive by blending charge components to achieve viscosity levels suitable for temperature selective conversion to lube oil product commensurate with the relationships established by the curves of FIGS. 1 and 2.

United States Patent Smith Sept. 2, 1975 [54] METHOD FOR PRODUCING2,960,458 11/1960 Beuther et a1. 208/19 HYDROCRACKED LUBE OIL PRODUCTS3,046,218 7/1962 Henke ct a1. 3,142,634 7/1964 Ireland et a1...Inventor: Fritz A. Smith, Haddonfield, NJ. 3, ,055 3 1967 white er a].3,493,493 2/1970 Henke et a1. [73] Assignee. Mobil Oll Corporation, NewYork, 3.506565 4/1970 white et aL 3,579,435 5/1971 Olenzak et a1. 208/59[22] Filed: Sept. 5, 1974 Primary Examiner-Delbert E. Gantz 1211 Appl'5031239 Assistant Examiner-G. E. Schmitkons Rdated U Appncation DataAttorney, Agent, or F irm-Charles A. Huggett; Carl D. [63]Continuation-impart of Scr. No. 2,764, Jan. 14, Famsworth 1970,abandoned.

[57] ABSTRACT [52] US. Cl. 208/; 208/19; 208/1 1 l The production oflube oil product by hydrocracking [51] Int. Cl... C01g 37/02; ClOg13/02; ClOg 31/14 is made more selective and commercially attractive by[58] Field of Search 208/110, 111, 18, 19 blending charge components toachieve viscosity levels suitable for temperature selective conversionto [56] References Cited lube oil product commensurate with therelationships UNITED STATES PATENTS established by the curves of FIGS. 1and 2. 2,917,448 12/1959 Beuther ct a1. 208/57 5 Claims, 3 DrawingFigures LUBE OIL HYDROCRACKING EFFECT OF CHARGE STOCK VISCOSITY ON LUBEOIL VISCOSITY VISCOSITY OF CHARGE STOCK, SSUQ 210' F. (:1 o o Conditions2500psiq,O.4LHSV, aoooscru 1B CHARGE STOCK VISCOSITY,SS O 210 F.

9 W-TEXAS HVGO 64 WTHVGO/WTPDR 92 Q WTHVGO/WTPDR 20 POUR LUBE VISCOSITY,SS U(0 IOOF.

PATENTEU SEP 2 5 SHIN 3 OF 70 so 90 I00' FIGURE 5 Age/1f 1 METHOD FORPRODUCING I-IYDROCRACKED LUBE OIL PRODUCTS This is acontinuation-in-part of application Ser. No. 2.764 filed Jan. 14, 1970.now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to thepreparation of lubricating oils. A number of processing arrangementshave been proposed in the prior art for producing lubricating oils fromless suitable hydrocarbon charge stocks by catalytic conversion.hydrogenation processes. clay treating, solvent extraction andcombinations thereof. Catalytic conversion processes and particularlycatalytic hydrocraeking or hydrogenolysis can be defined as catalyticcracking in the presence ofa hydrogen atmosphere to accomplishsignificant reductions in the molecular weight of the charge stock.Hydrocracking is distinguishable from hydrotreating and hydrofinishingby the amoutn of molecular weight reduction and hydrogenconsumption-Generally, a hydrofinishing operation consumes less hydrogenthan hydrotreating and hydrotreating consumes less hydrogen thanhydrocraeking.

To produce a refined lubricating oil by conventional solvent extractiontechniques of desired viscosity index, it has been necessary to employas a feed. an oil which already has a higher viscosity and lower VI thanthat desired. Thus high quality crude oils were segregated on a largemass basis for use in preparing lower viscosity but higher viscosityindex lube oil products whether by hydrofining operations or by chemicaltreatment such as by extraction with solvents. The prior art processesare generally less than satisfactory since each was designed to operatefor the production of a particular type of lubricating oil product andoffering little versatility in operation. Thus numerous economicrestrictions are imposed by such processes. Catalytic processesoperating at elevated temperatures and pres sures are quite expensiveand difficult to justify economically except when based on processinglarge quantities of charge material or unless a tremendous upgrading inthe value of the products produced is obtained. Thus in a severehydrogenation process such as obtained by destructive hydrogenation orhydrocraeking where distillate fuels of high value are produced, it wasnecessary to control the operation of the process under prior artpractices so as to obtain a major amount of a general range of lube oilproducts produceable from the charge. Thus the quality and quantity ofthe lube 'oil product comes by happenstance rather than by design andspecific control.

THE INVENTION The present invention is concerned with the preparation ofparticular lube oil products by a selective hydrocraeking operationdesigned to satisfy predetermined viscosity requirements Such'asrequired for high performance motor oils known as automotive gear oils.circulation oils. industrial hydraulic oilsrand other specialtylubricating oil products.

One'of the important specifications of a lubricating oil is itsviscosity, that is. the resistance to deformation of the liquid whensubjected to a shear stress. The present invention isparticularlyconcerned with the preparation of lube oil products having particularlydesired viscosity rating by exercising a particular control over theviscosity of the'chargc stock converted by the process and over thetemperature at which particular conversion occurs. A very effectivemethod for exercising control on the viscosity of the charge stock is bya selective blending of charge stocks of different viscosities. Aneffective method for exercising selective control on the conversiontemperature is to use the viscosity of the 650F waxy lube oil product asa basis to relate and regulate particularly the inlet temperature to thehydrocracker.

DESCRIPTION OF THE DRAWINGS FIG. 1 presents a family of VI (viscosityindex) curves which show a relationship found to exist between thecharge stock viscosity and a 20F. pour point lube oil product viscositymeasured as SSU at l()()F.

FIG. 2 presents a family of V] (viscosity index) curves which show arelationship found to exist between the charge stock viscosity and a20F. pour point lube oil product viscosity measured as SSU at 210F.

FIG. 3 identifies a blending chart showing the relationship existingbetween high and low viscosity oils for blending to produce a particularviscosity product.

DESCRIPTION OF SPECIFIC EMBODIMENTS In a particular aspect. the methodand technique of the present invention has been demonstrated by blendinglow viscosity West Texas Sour Heavy Vacuum Gas Oil (WTSHVGO) with highviscosity West Texas Sour PD Raffinate (WTSPDR). For instance, WestTexas Sour Heavy Vacuum Gas Oil (64 SSU at 2l()F) results in a dewaxed65()"F pool viscosity of 43 SSU at 2 l 0F. after hydrocraeking to l25V.I. However. the desired pool viscosity for this product, on the otherhand, is 48 SSU at 210F. rather than 43 for V.I. material. This desiredpool viscosity of 48 can be attained, it has been found, by blending aWest Texas Sour PD Raffinate I60 SSU at 210F.) with the West Texas SourHeavy Vacuum Gas Oil until the charge blend viscosity is about 116 SSUat 210F. This blend is then hydrocracked to 125 VI. to produce thedesired 48 SSU product. Thus the concept of the present invention isconcerned with selecting particular charge stock materials of suitableviscosity so that through selective blending thereof and/or control of avacuum tower or other distillation means a particular charge stockviscosity can be obtained which upon hydrocraeking will provide aproduct of desired viscosity. This selective method of operation reduceslosses attributed to overcracking and processing large excesses ofcharge material to obtain a particular viscosity-VI product.

In general, most charge stocks suitable for use in a lube oilhydrocraeking process are heavy materials such as vacuum gas oils andpropane deasphalted raffinates. However other charge materials may beemployed such as slack wax, petrolatum and even cracked gas oils canalso be employed to advantage depending on the product desired. Chargestocks high in asphaltene content are less desirable because of theireffect on catalyst aging and suspected adverse effect on productquality.

The type of compounds or components required in lube oil base stocks toattain a high viscosity index are known and discussed in the literature.In general, paraffin's, ring compounds (especially monoanddicycliccompounds) in which the rings are fully saturated,alkylbenzencs. alkyltetralins and some alkyl naphthalenes are desirablecomponents. Unsaturated condensed ring compounds are less desirablesince they have very low viscosity indexes. Normal paraffins, on theother hand, have high V.l.s but also have a high pour point which is anundesirable factor.

The method of the present invention is concerned with convening as manyof the undesirable types of compounds or complex molecular structuresfound in lube oil charge stock into molecular structures having desiredviscosity index and viscosity. This type of conversion can be done, ithas been found, with good selectivity by use of a proper catalyst incombination with a proper charge material at selective operatingconditions.

It has been observed further that the path of reaction during suchconversion by which the undesirable components in, for example, a KuwaitPD Raffmate, may be converted into desired quality lube oil base stockscan be predicted. Thus it was found that the composition of the chargechanges the space velocity is decreased when the hydrogen partialpressure is 2,500 psig and the temperature is 775F. For example,paraffms are found to increase monotonically; monoand di-nuclearnaphthenes increase gradually, reach a maximum at a space velocity ofabout 0.9 and then decrease rapidly as space velocity decreases. Monoanddi-nuclear aromatics increase rapidly, reach a maximum at a spacevelocity of three, and then decrease as space velocity decreases.Polynuclear naphthenes increase gradually, reach a maximum at a spacevelocity of about 2.5. and then gradually decrease as space velocitydecreases. Polynuclear aromatics decrease monotonically and so do theresins and asphaltenes. The extent of all these chemical reactions isreflected in the viscosity of the product as shown on the attachedfigures.

It has been found that with substantially any hydrocarbon charge stockthe V.l. (viscosity index) increases but yield decreases as thehydrocracking reaction se verity is increased, thus resulting in anundesired in creased conversion to, for example. lower boiling products.In the present discussion, conversion is based primarily as a matter ofconvenience on a 650F. cut point but other cut points, such as 600F. orup to 700F. would be suitable in some instances with appropriateadjustments. The yield of 650F waxy conversion product was correlated tothe V.l. of the 650F dewaxed oil. It was observed from the resultsobtained that the V.l. increases as conversion increases, reaches amaximum and then decreases as conversion continues to increase. Theregion of decreasing V.l. is construed as over-cracking" although thismay be viewed as a misnomer by some.

As severity of the hydrocracking reaction or conversion is increased byeither increasing temperature or decreasing space velocity, theviscosity index increases as yields of (60F product material decreaseand the viscosity also decreases. On the other hand, as the conversionincreases and the 650F yields decrease, the change in viscosity of the650F waxy or dewaxed oil becomes less and appears to approach anequilibrium value which is found quite unexpectedly to be charge stockdependent.

Thus temperature has a significant effect on 650F lube yields, viscosityand viscosity index (V.l. If the space velocity is increased, however,then the temperature must also be increased to maintain the V.l. level.Temperatures should be maintained within the range of 700 to 850F. andpreferably should be from about 720F. to about 800F. Thus, in order tomaximize yield of the waxy 650F product material it is desirable toemploy as low a space velocity as possible commensurate with acceptabletemperature operating conditions in the range of from about 700F. toabout 850F. A space velocity in the range of0.25 up to about 3.0 may beemployed. However, it is preferred that the space velocity be maintainedin the range of 0.4 to about I .5. Pressure has also been found to havea significant effect on the yield structure at constant V.l. Forexample, decreasing the hydrogen pressure by 500 psig decreases the waxy650F product yield as much as 5 or more volume percent. At the lowerpressure, hydrogen consumption is slightly lower and so is theviscosity. Thus the hydrogen partial pressure should be retained withinthe range of from about L800 to about 3,000 psig and more preferablyshould be within the range of 2,200 to about 2,800 psig.

FIGS. 1 and 2 presented herewith are essentially selfexplanatory. Theydiffer from one another in that FIG. 1 applies when the 20F. pour pointlube oil viscosity is measured as SSU at I00F. whereas FIG. 2 applieswhen the viscosity is measured as SSU at 210F. It will be observed uponexamination of the figures that for a given V.l. material, the viscosityof the product varies as the viscosity of the charge varies.

FIG. 3 provides a blending relationship between low and high viscositymaterials and identifies the amount of each of these materials to beblended with one another to produce a blended charge material ofpredetermined desired viscosity requirement which will provide uponselected hydrocracking severity conditions, a product of desired V.l.and viscosity. From FIG. 3, it will be observed by way of exampleidentified by the dotted lines that blending a 40 viscosity materialwith a 200 viscosity material (Universal Saybolt Scale) requires about64 percent of the high viscosity oil in the blend to produce a blendedmaterial having a viscosity of about 83 or 84. Hydroeraeking such ablended product-charge under severity conditions selected to produce aI25 V.I. product is shown by FIG. 1 to produce a product of I50viscosity as measured on the SSU scale at I00F. However, when measuredat 210F. FIG. 2 shows that the product will have a viscosity of onlyabout 44.40.

The specific embodiments herein discussed have established that arelationship exists between specific charge stocks and product obtainedwhen using a CMZS (cobalt-molybdenum-zirconium-silica) catalystcomposition for hydrocracking which clearly demonstrates the concept ofthe present invention. It is to be noted, however, that differenthydrocracking catalyst compositions will effect the severity of ahydrocracking operation for any given pressure, temperature and spacevelocity condition selected. Allowance for this difference must be madewhen employing a different catalyst. Also. the family of curves andrepresentationpresented in FIGS, I and 2 will vary to some extentdepending upon the charge stocks employed as well as the catalystcomposition used to effect the hydrocracking operation. However, arelationship or correlation remains and substantially any knownhydrocracking composition may be employed in practising the concept ofthe present invention. A suitable hydrocracking catalyst will includeone or more hydrogenation components selected from the group comprisingthe sulfides and oxides. or mixtures thereof, of the metals of Groups VIand VII dispersed on a suitable carrier material. The carrier materialmay be a silicious cracking component or it may be an alumina base whichis active under the conditions employed. The carrier material mayinclude composites such as silica-alumina. silicatitania.silica-zirconia, silica-magnesia or other silicious base carriercompositions.

In addition to the above, the present invention contemplates controllingthe hydrocracking reaction by mechanism commensurate with identificationof particularly desired products. Thus in one embodiment it iscontemplated employing the 600F. or 650W product viscosity before orafter dewaxing as a control function to control the outlet temperatureof the preheat furnace used in a hydrocracking process to raise thetemperature of the hydrocarbon charge to a desired inlet reactiontemperature. In addition, the above identified viscosity controlfunction may be employed to control the exothermic hydrocrackingreaction temperatures within desired limits by employing the controlfunction to control the amount of quench fluid such as quench hydrogenor recycle gas introduced to the hydrocracking reactor between catalystbeds,

Having thus provided a general discussion of the present invention andprovided specific examples in support thereof, it is to be understoodthat no undue restrictions are to be imposed by reasons thereof exceptas provided by the following claims.

I claim:

I. In a process for producing 650"F waxy lube oils of desired viscosityby hydrocracking a hydrocarbon charge stock in the presence of ahydrocracking catalyst at a temperature within the range of 700 to850F., a space velocity within the range of 0.25 to 3.0 and a hydrogenpartial pressure within the range of L800 to 3,000 psig, the improvementfor reducing the volume of hydrocarbon charge to the process whichcomprises,

selecting from the relationship provided by FIG. 1

and 2 the viscosity of the charge stock required to produce a product ofdesired viscosity and viscosity index,

blending charge stocks of different viscosityin accordance with therelationship provided by FIG. 3 to form a charge stock of desiredviscosity as determined from FIGS. 1 and 2,

hydrocracking the blended charge stock within the processing limitsabove identified and using the viscosity of the 650F waxy lube oilproduct as a basis for exercising a selective control on the conversiontemperature.

2. The process of claim 1 wherein the hydrocracking temperature ismaintained within the range of 720800F.

3. The process of claim I wherein the hydrocarbon space velocity iswithin the range of 0.4 to L5.

4. The process of claim 1 wherein the hydrogen partial pressure ismaintained within the range of 2,200 to 2,800 psig.

5. The process of claim 1 wherein the hydrocracking catalyst comprisescobalt-molybdenum-zirconium and silica. I

1. IN A PROCESS FOR PRODUCING 650*F+ WAXY LUBE OILS OF DESIRED VISCOSITYBY HYDROCACKING A HYDROCARBON CHARGE STOCK IN THE PRESENCE OF AHYDROCRACKING CATALYST AT A TEMPERATURE WITHIN THE RANGE OF 700* TO850*F, A SPACE VELOCITY WITHIN THE RANGE OF 0.25 TO 3.0 AND A HYDROGENPARTIAL PRESSURE WITHIN THE RANGE OF 1,800 TO 3,000 PSIG, THEIMPROVEMENT FOR REDUCING THE VOLUME OF HYDROCARBON CHARGE TO THE PROCESSWHICH COMPRISES, SELECTING FROM THE RELATIONSHIP PROVIDES BY FIG. 1 AND2 THE VISCOSITY OF THE CHARGE STOCK REQUIRED TO PRODUCE A PRODUCT OFDESIRED VISCOSITY AND VISCOSITY INDEX, BLENDING CHARGE STOCKS OFDIFFERENT VISCOSITY IN ACCORDANCE WITH THE RELATIONSHIP PROVIDED BY FIG.3 TO FORM A CHARGE STOCK OF DESIRED VISCOSITY AS DETERMINED FROM FIGS, 1AND 2, HYDROCRACKING THE BLENDED CHARGE STOCK WITHIN THE PROCESSINGLIMITS ABOVE IDENTIFIED AND USING THE VISCOSITY OF THE 650*F+ WAXY LUBEOIL PRODUCT AS A BASIS FOR EXCERCISING A SELECTIVE CONTROL ON THECONVERSION TEMEPERATURE.
 2. The process of claim 1 wherein thehydrocracking temperature is maintained within the range of 720*-800*F.3. The process of claim 1 wherein the hydrocarbon space velocity iswithin the range of 0.4 to 1.5.
 4. The process of claim 1 wherein thehydrogen partial pressure is maintained within the range of 2,200 to2,800 psig.
 5. The process of claim 1 wherein the hydrocracking catalystcomprises cobalt-molybdenum-zirconium and silica.